Method for bonding a porous medium to a substrate

Abstract

A method for bonding a porous medium to a substrate is provided which includes contacting a porous medium with a surface of a substrate, impregnating the porous medium with a bonding composition, maintaining the impregnated porous medium in contact with the substrate surface until the substrate surface is at least slightly dissolved in the bonding composition without dissolving the porous medium, and passing the bonding composition through the impregnated porous medium towards the substrate and subsequently away from the surface of the substrate to remove bonding composition containing dissolved substrate from a portion of the porous medium to minimize blockage of pores in the porous medium.

I claim: 
     
       1. A method for bonding a porous medium to a substrate comprising: contacting a porous medium with a surface of a substrate;   impregnating the porous medium with a bonding composition which at least slightly dissolves the substrate surface without dissolving the porous medium;   maintaining the impregnated porous medium in contact with the substrate surface until the substrate surface is at least lightly dissolved in the bonding composition;   flushing at least a portion of the bonding composition through the impregnated porous medium towards the substrate and subsequently away from the surface of the substrate to remove bonding composition containing dissolved substrate from a portion of the porous medium to minimize blockage of pores in the porous medium; and   evaporating the bonding composition from the substrate and the porous medium.   
     
     
       2. The method of claim 1 wherein contacting the porous medium and the substrate surface includes contacting a dry porous medium with the surface of the substrate. 
     
     
       3. The method of claim 1 wherein flushing the bonding composition comprises applying a vacuum to the side of the porous medium in contact with the substrate. 
     
     
       4. The method of claim 1 wherein evaporating the bonding composition comprises applying a vacuum to the substrate and the porous medium. 
     
     
       5. The method of claim 1 further comprising contacting the porous medium with a porous pad and wherein impregnating the porous medium with the bonding composition comprises applying the bonding composition to the pad and transferring at least a portion of the bonding composition from the pad to the porous medium. 
     
     
       6. The method of claim 5 wherein the porous pad includes a compressible, porous material, which is inert to the bonding composition. 
     
     
       7. The method of claim 5 further comprising contacting the porous pad With a highly liquid permeable structure and wherein applying the bonding composition to the pad comprises applying the bonding composition to the highly liquid permeable structure and transferring at least a portion of the bonding composition from the highly liquid permeable structure to the pad. 
     
     
       8. The method of claim 7 wherein the highly liquid permeable structure comprises metal woven mesh or plastic woven mesh. 
     
     
       9. The method of claim 7 wherein the total voids volume of the pad and the highly liquid permeable structure is at least about equal to the voids volume of the porous medium. 
     
     
       10. The method of claim 7 wherein the total voids volume of the pad and the highly liquid permeable structure is from about one and to about thirty times the voids volume of the porous medium. 
     
     
       11. The method of claim 1 comprising contacting the porous medium with the substrate surface, wherein the substrate comprises a polyethersulfone, a polysulfone or a polyamide. 
     
     
       12. The method of claim 1 comprising contacting the porous medium with the substrate surface, wherein the porous medium comprises a polyamide, a fluoropolymer, a polyethersulfone, an acrylic, a polyester or a cellulose ester. 
     
     
       13. The method of claim 12 wherein the porous medium comprises nylon, poly(vinylidene difluoride) or polytetrafluoroethylene. 
     
     
       14. The method of claim 12 wherein the porous medium comprises nylon-46, nylon-6, nylon-66 or nylon-610. 
     
     
       15. The method of claim 1 comprising contacting the porous medium with the substrate surface, wherein the porous medium comprises a microporous filter medium. 
     
     
       16. The method of claim 15 wherein the microporous filter medium comprises a microporous fibrous matrix or a microporous membrane. 
     
     
       17. The method of claim 1 wherein flushing the bonding composition includes directing fluid away from the surface of the substrate through grooves in the substrate surface. 
     
     
       18. The method of claim 1 wherein flushing the bonding composition includes directing fluid away from the surface of the substrate through interconnecting pores in the substrate surface. 
     
     
       19. A method for bonding a porous medium to a substrate comprising: contacting a porous medium with a surface of a substrate;   impregnating the porous medium with a bonding composition;   maintaining the impregnated porous medium in contact with the substrate surface until the substrate surface is at least slightly dissolved in the bonding composition without dissolving the porous medium; and   passing the bonding composition through the impregnated porous medium towards the substrate and subsequently away from the surface of the substrate to remove bending composition containing dissolved substrate from a portion of the porous medium to minimize blockage of pores in the porous medium.   
     
     
       20. A method for bonding a porous membrane to a substrate comprising: contacting a dry porous nylon membrane with a dry surface of a polyethersulfone substrate;   contacting the porous membrane with a compressible, porous pad;   applying a bonding composition, which includes methylene chloride and methanol, to the pad and transferring at least a portion of the bonding composition from the pad to the porous membrane, thereby impregnating the porous membrane with the bonding composition;   maintaining the impregnated porous membrane in contact with the substrate surface until the substrate surface is at least slightly dissolved in the bonding composition without dissolving the membrane;   flushing at least a portion of the bonding composition through the impregnated porous membrane toward the substrate and subsequently away from the surface of the substrate through interconnecting grooves in the surface by applying a vacuum to the substrate surface to remove bonding composition containing dissolved substrate from a portion of the porous medium add minimize blockage of pores in the porous medium; and   then evaporating the bonding composition from the substrate and the porous membrane by applying a vacuum to the substrate and the membrane, thereby removing the methylene chloride more rapidly than the methanol such that the bonding composition no longer dissolves the substrate.